Mercedes arrived at the Canadian Grand Prix with its first major upgrade package of the season. The team of championship leader Kimi Antonelli and George Russell revised, among other things, the front wing and floor, although rivals also took an interest in several solutions at the rear of the W17.
Since winter testing, teams have been trying to find clever ways to extend the diffuser, for example by introducing extensions attached directly to the rear crash structure. Making the diffuser work as effectively as possible is a crucial aspect, especially now that the current generation of cars relies less on ground effect.
Frederik Vesti, Mercedes
Photo by: Sam Bloxham / LAT Images via Getty Images
The diffuser Mercedes introduced in Montreal particularly caught the eye because of several additions on its upper section – in the form of spike-like profiles. Mercedes added serrated profiles along the upper section of the W17’s diffuser, covering more than half of its width. Their purpose was effectively to extend the diffuser and enhance its effect.
After Ferrari and several other rivals spotted the solution, the Scuderia asked the FIA for clarification and raised the question of whether it would be allowed to develop a similar design, but was not given the green light to do so.
Motorsport.com has learned that the FIA mainly wanted to clarify its stance, as the Mercedes upgrade could open the door to more creative solutions that the governing body would not be comfortable with.
Lewis Hamilton, Ferrari
Photo by: Andy Hone/ LAT Images via Getty Images
That led to a technical directive following the Barcelona Grand Prix, a document that comes into force from the Austrian Grand Prix weekend onwards.
As of 2026, such a document is referred to as an FIA doc rather than a technical directive, although that is just for consistency purposes, as an FIA doc can cover all areas from sporting matters to technical ones.
Mercedes has acknowledged that, in line with the new guidelines issued after Barcelona, some ‘minor tweaks’ to the diffuser were required, and those changes were already visible during media day in Austria in various photos.
The diffuser extensions are still on the W17 to a certain extent, but without the spike-like profile. Apart from Mercedes, Racing Bulls has also been asked to change its diffuser extensions.
The current situation still leaves some room to explore this area in a less extreme way, which has been confirmed by other teams in the paddock. They explain that while the way Mercedes implemented the trick on its Montreal-spec diffuser is now prohibited, virtually all teams are still exploring ways to effectively extend the diffuser.
Ferrari car tech detail
Photo by: Richard Byles / Getty Images
That can also be seen in images of Ferrari’s 2026 challenger. The image above shows extensions on the diffuser of the SF-26. Customer team Haas uses a similar concept, albeit with multiple elements.
Those solutions – just like Mercedes’ revised Austria spec – fall within the boundaries of what is permitted, although the FIA wanted to close the door to more extreme designs going forward.
Photos from Austrian GP – Thursday
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– The Autosport.com Team
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